Factor acentric

One important parameter presented in the EOS is the acentric factor co. The acentric factor is used to correlate physical and thermodynamic properties. Mathematically, the acentric factor is defined as [9]  

Other important factors used to establish physical and thermcxlynamic properties of hydrocarbon mixtures are the Watson characterization factor K and critical compressibility factor z. Table 1.13 presents values of the acentric factor, the Watson characterization factor, and the critical compressibility factor. A complete list is available in the API Technical Data Book [9]. 

The fugacity coefficient of a pure component is estimated differently by SRK and PR EOSs. 

As discussed in Section 2.5.4, the simple two-parameter corresponding states principle indicates that a generalized equation of state for all substances can be created using only two specific parameters, for example, T, and P. The success of this approach is restricted to simple, spherical molecules like Ar, Kr, Xe, or CH4, where vapor pressure and compressibility factor can be reasonably described. For other molecules, the simple two-parameter corresponding states principle leads to significant errors. A large improvement has been achieved with the introduction of a third parameter which describes the vapor pressure curve (extended three-parameter principle of corresponding states). The most common parameter of this kind is the so-called acentric factor, which is defined as 

The physical meaning of this parameter is the description of orientation-dependent intermolecular interactions. The parameter is used in many correlations for the estimation of thermophysical properties, especially in cubic equations of state. The definition makes sense, as vapor pressures as a function of temperature are 

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REDUCED DIPOLE MOMENT PRIME. ALSO. REDUCED DIPOLE MOMENT IN EARLIER PART OF THE PROGRAM. EFFECTIVE NON-PQLAR ACENTRIC FACTOR. 

The acentric factor is calculated using Edmister s equation (1948) ... 

Pseudo Critical Constants and Acentric Factors for Petroleum Fractions... 

The estimation of the three parameters —pseudo-critical temperature, pseudo-critical pressure, and the acentric factor— should be done using the same method because these constants should be coherent. 

When the reduced boiling point is greater than 0.8, it is not recommended to use the conventional formula [4.3]. The acentric factor should be estimated by the following relation ... 

According to this concept, a reduced property is expressed as a function of two variables, and I/, and of the acentric factor, cd ... 

The critical molar volume is defined using the acentric factor by the following, relations . 

I 0) = acentric factor of the mixture 0)- = acentric factor of component /... 

The pseudocritical compressibility factor is obtained directly from the i acentric factor using the expression ... 

Hexane, for example, is a component whose properties are well known and follow the principle of corresponding states very closely. The acentric factor recommended by the DIPPR is 0.3046 and is considered by convention not to vary with temperature. 

The acentric factor can be determined as a function of temperature by finding the exact properties supplied by the DIPPR. 

If the vapor pressure is of interest, the acentric factor is calculated by the Lee and Kesler formula or by the Soave method, which are given in article 4.5.2. 

The values obtained for the acentric factor differ significantly from one another. As shown in Figure 4.3, this factor depends on the temperature, the physical property being considered, and the method used. 

Hexane is an easy example. The variations in acentric factors are much more pronounced for heavy polar or polarizable components. It comes as no surprise that the values reported from different sources are not identical. 

The acentric factor is also dependent on the critical coordinates being used. 

To avoid confusion, the only acentric factor that we will use is that employed to find the boiling point by the Lee and Kesler method. 

This method utilizes essentially the concept developed by Fitzer in 1955. According to the principle of three-parameter corresponding states, the compressibility factor z, for a fluid of acentric factor w, is obtained by interpolating between the compressibilities Zj and Z2 for the two fluids having acentric factors w, and (p -... 

R = ideal gas constant dCp = reduced correction for C, a function of and and of the acentric factor... 

Soave also proposed a formula to calculate the constant, m, as a function of the.acentric factor ... 

Soave m coefficient Solubility parameter at 25°C 0iJ/m ) /2 Temperature n °c Interfacial tension at mN/m Lee Kesier acentric factor... 

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